Titanium dioxide with aluminum oxide or aluminium oxide plus silicon dioxide precipitated thereon as pigment for diffusion transfer

ABSTRACT

Photographic diffusion transfer reversal process in which a positive diffusion transfer reversal image is formed in a lightsensitive monosheet material, wherein said image is made visible against a white pigment layer that covers the negative image produced in the monosheet, wherein said white pigment layer contains a white titanium dioxide pigment that has been modified by precipitation thereon of hydrated aluminium oxide or of hydrated aluminium oxide together with hydrated silicon dioxide.

United States Patent [191 De Haes et al.

[451 Dec. 23, 1975 TITANIUM DIOXIDE WITH ALUMINUM OXIDE OR ALUMINIUM OXIDE PLUS SILICON DIOXIDE PRECIPITATED THEREON AS PIGMENT FOR DIFFUSION TRANSFER Inventors: Innis Maria De I-Iaes, Edegem,

Belgium; Hans-Georg Viilz, Krefeld-Bockum, Germany AgIa-Gevaert N.V., Mortsel, Belgium Filed: May 15, 1974 Appl. No.: 470,271

Assignee:

Foreign Application Priority Data May 16, 1973 Germany 2324590 US. Cl 96/29 R; 96/3; 96/29 D; 96/76 R; 96/77; 96/84 R Int. Cl. G03C 5/54; 003C 7/00; 603C 1/48; G03C l/40 Field of Search 96/76 R, 29 R, 84 R, 29 D, 96/3 [56] References Cited UNITED STATES PATENTS 2,627,459 2/1953 Land 96/29 R 3,615,520 10/1971 Land..... 96/76 R 3,721,556 3/1973 Fix 96/84 R FOREIGN PATENTS OR APPLICATIONS 1,164,849 9/1969 United Kingdom Primary Examiner-Charles L. Bowers, Jr. Assistant Examiner-Richard L. Schilling Attorney, Agent, or Firm--William J. Daniel ABSTRACT 25 Claims, No Drawings TITANIUM DIOXIDE WITH ALUMINUM OXIDE OR ALUMINIUM OXIDE PLUS SILICON DIOXIDE PRECIPITATED THEREON AS PIGMENT. FOR DIFFUSION TRANSFER The present invention relates to a material and process for the production of visible images by diffusion transfer reversal.

In the published German Patent Application No. 1,772,603 filed June 7, 1968 by Gevaert-Agfa N.V. a photographic light-sensitive composite sheet material for the production of images according to the silver complex diffusion transfer reversal process has been described. This sheet material comprises successively a non-transparent flexible support, a light-sensitive silver halide emulsion layer, and a layer comprising an opaque white or coloured pigment and a hydrophilic colloid binder. When the transfer image obtained is viewed, the negative image in the silver halide emulsion layer cannot be seen since it is screened off by the pigment layer, lying between the image-receiving layer and the silver halide emulsion layer.

In the US. Pat. No. 2,627,459 of Edwin H. Land issued Feb. 3, 1953 a photographic composite sheet material is described, which comprises successively a support e.g. a cellulose film support or a baryta paper support, a light-sensitive silver halide emulsion layer, and a transparent image-carrying layer e.g. a cellophane foil that is permeable to water vapour. Between the light-sensitive layer and the image-carrying layer a pod or container is provided, which contains a liquid processing composition that 'also forms the imagereceiving layer. This processing composition also contains opaque white pigment particles. After the imagewise exposure through the transparent image-carrying layer the composite film material is fed between a pair of pressure rollers, the container end entering first. The pressure rollers break the container and spread the liquid composition uniformly between the lightsensitive layer and the image-carrying layer. The image-receiving layer is formed from this liquid composition. The latter layer shows the diffusion transfer image through the image-carrying layer on a white background obtained by the presence of the opaque white pigment particles in the image-receiving layer.

Other photographic materials and processes for the production ofa so-called composite image according to the silver complex diffusion transfer reversal process are described in the published German Patent Applications Nos. 1,572,024, 1,572,025 both filed Jan. 11, 1967 by lntern. Polaroid Corp. and No. 1,961,030 filed Dec. 5, 1969 by Gevaert-Agfa N.V. By composite image we understand a composite print, in which a positive image is formed in an overlayer covering the negative image. The composite print can then be viewed as a positive reflection print (non-transparent printlwithout separation of both-images. For this purpose the negative silver image is covered effectively by an opaque layer, whose opacity preferably does not suffice toprevent the image-wise exposure of the silver halide through the pigment layer and yet gives a suffinot any titanium dioxide pigment is suited for use in the above described photo-materials.

A number of commercial titanium dioxide pigments have the disadvantage of bringing about an unpleasant marked brown staining in the finished paper. The reason of this brown staining could be a further reaction of the developing chemicals, which is catalyzed by certain surface properties of the titanium oxide pigments used. Tests have proved that the brown staining is not connected either with the rutile or anatase types. Indeed, it was found that both types can lead to the brown staining. This staining is especially disturbing in monosheet materials for the production of photographic images, when a treatment with aqueous baths, in particular rinsing with water, is not provided, so that all of the developing chemicals and their reaction products remain within the layer structure.

The same difficulties are encountered when by means of similar monosheet materials colour transfer images have to be produced'by diffusion transfer of dyes. I

Preferably the colour transfer image should be visible on a white background and the original light-sensitive negative layers'should become invisible and shielded ciently white background to allow the viewing of the positive image as a reflection print.

In the above materials and processes titanium dioxide pigment particles are used as opacifiers to produce the desired opacity. It has been found experimentally that from further-exposure. These purposes are attained by the use of a pigment layer, which at the latest in the finished image is present between the image-receiving layer and the originally light-sensitive layers. The pigment layer can be provided between the light-sensitive layers and the image-receiving layer already during the manufacture of the monosheet material, as has been described in the published German Patent Application No. 1,924,430 filed May 13 1969 by lnt. Polaroid Corp. According to another processthe pigment layer is produced between the light-sensitive layers and the image-receiving layer only during the processing step by pressing a'processing mass containing an opacifier between the above-mentioned layers. Depending on the nature of the colour-forming compounds used the negative layers to be covered show a relatively high colour density, so that particularly high standards are set to the covering power of the pigment layer in monosheet materials for the dye diffusion transfer process.

It has been proposed in the published German Patent Application No. 1,920,406 filed Apr. 22, 1969 by Int. Polaroid Corp. to eliminate the brown staining by using a polyol-treated titanium dioxide pigment as opacifier.

These polyol-treated titanium dioxide pigments as well as their preparation have been described detailedly in the US. Pat. No. 3,076,719 of Walter R. Whately and Gerard M. Sheehan issued Feb. 5, 1963. The stabilization of the brown staining is attributed to the presence of the polyols in the titanium dioxide pigment, which are added to the pigment in concentrations between 0.01 and 3% by weight. Experiments have shown, however, that a favourable stability to brown staining has nothing to do with the polyol content, but that other causes are decisive.

It is an object of the present invention to provide an opacifier for use in photographic monosheet materials, which does not give origin to a subsequent brown staining of the image background so that images having a permanent white image background are obtained.

It has been found now, that in a photographic monosheet material for the production of a composite image a titanium dioxide pigment can be used as an opacifier to cover the negative image effectively.'The titanium dioxide pigment used according to the present inven- The hydrated aluminium oxide (calculated in the form of A1 is used in an amount of e.g. 0.5 to 20% by weight and preferably of 0.5 to.5% by weight in respect of the titanium dioxide.

The hydrated silicon dioxide (calculated in the form of SiO is used in an amount of e.g. 0.1 to 20% by weight and preferably of 0.5 to 5% by weight in respect of the titanium dioxide.

It appears that the titanium dioxide pigments treated with SiO and A1 0 simultaneously are suited for the production of photographic materials having a high resistance to brown staining. The amount of hydrated aluminium oxide used is optional whereas at least some tenths of a percent of hydrated silicon oxide e.g. 0.5% by weight calculated on the titanium dioxide have to be precipitated together with the hydrated aluminium oxide.

The resistance to brown staining can be tested as follows. For this purpose materials for the production of a composite image according to example 1 of the published German Patent Application No. 1,772,603 as mentioned hereinbefore are prepared. Only the type of the titanium dioxide is changed for each test material.

The material is prepared in the following way: a non-transparent paper sheet weighing 90 g/m2 is coated with a high-sensitive ortho-sensitized silver chloride gelatin emulsion containing hydroquinone and l-phenyl-3-pyrazolidinone in such a way that a silver halide emulsion-layer is obtained, which contains per sq.m a silver chloride amount that is equivalent to 0.5 g of silver nitrate, 0.2 g of hydroquinone, and 0.05 g of l-phenyl-3-pyrazolidinone.

The light-sensitive silver halide emulsion layer is coated with the following pigment layer composition covering 12 sq.m:

parts by volume of water The resulting pigment layer is then covered at a ratio of 1 1/45 sq.m with the following composition containing development nuclei:

water 980 ml aqueous dispersion containing 0.6 of nickel sulphide and 1.9 of gelatin ml 12.5 solution of saponin in a mixture of parts by volume of ethanol and 80 parts by volume of water (the mentioned percentages are by weight) The materials for the production of a composite image are stuck in the form of strips having a width of approximatively 5 cm and a length of approximatively 30 cm side by side on a support and exposed some 5 min. to daylight or artificial light. In this way a subse- 4 quent diffusion (during the processing) of the unexposed silver is avoided.

Next, a number of some 7 strips are fed together through a processing apparatus commonly used for silver halide diffusion transfer materials, the apparatus having been filled with an activator having the following composition:

water 800 ml SEQUESTRENE (trade name) Na (the tetrasodium salt of ethylene diamine tetraacetic acid) 2 g trisodium orthophosphate 12 H 0 g anhydrous sodium sulphite 40 g potassium bromide 0.5 g anhydrous sodium thiosulphate 10 g 1-phenyl-5-mercaptotetrazole 40 mg water to make 1000 m1 When leaving the squeegeeing rollers of the processing apparatus the strips are put in a translucent polyethylene bag having a thickness of pm. The bag is sealed hermetically by means of adhesive tape. One half of the bag is covered with black paper (or black polyethylene) in such a way that each strip is covered partially at its emulsion side and is not shielded from light at the other part.

The whole polyethylene bag is then placed between two glass plates and pressed close therewith. The whole is then placed under an ultraviolet lamp and irradiated for 3 min. by means of a Philips 572038 B/OO HPK W (trade name) mercury vapour lamp placed at a distance of 40 cm.

At the end of the irradiation the covering paper is removed and the staining is examined. The areas exposed to ultraviolet radiation of each strip are compared with the unexposed parts.

Five degrees of appreciation of the stability are taken:

Degree 1: very good (no staining can be observed) Degree 2: good (slight staining) Degree 3: satisfactory (medium staining) Degree 4: defective (strong staining) Degree 5: unsatisfactory (very strong staining).

In the following examples the pigments used according to the invention and the tests pertaining thereto are described more detailedly.

EXAMPLE 1 A non after-treated rutile pigment prepared according to the sulphate process was incorporated into a sheet material according to example 1 of the published German Patent Application No. 1,772,603 as mentioned hereinbefore and tested as described hereinbe- 5 fore. The paper showed a very strong staining. Result of the test: degree 5 (unsatisfactory).

' EXAMPLE 2 EXAMPLE 3 A rutile pigment after-treated with hydrated aluminium oxide (equivalent to 5% of A1 0 and prepared according to the sulphate process was tested as described in example 1. The paper showed only a faint staining. Result of the test: degree 2 (good)..

EXAMPLE 4 An anatase pigment after-treated with hydrated silicon dioxide (equivalent to 2% of SiO and hydrated aluminium oxide (equivalent to 5% of A1 and prepared according to the sulphate process was tested as described in example 1. The paper showed no staining. Result of the test: degree 1 (very good).

EXAMPLE 5 A rutile pigment after-treated with hydrated silicon dioxide (equivalent to 1% of SiO and hydrated aluminium oxide (equivalent to 2.5% of A1 0 and prepared according to the sulphate process,'was tested as described in example 1. The paper showed no staining. Result of the test: degree 1 (very good).

The preparation of titanium dioxide pigments according to the known sulphate or chloride process has been described in e.g. Ullmanns Enzyklopadie der technischen Chemie, 3rd Edition, Part 13 (1962) p. 760 to 768.

The titanium dioxide enveloped by aluminium oxide and/or silicon dioxide can be prepared as described in the United Kingdom Patent Specification No. 1,164,849 filed Dec. 1, 1966 by National Lead Co. or in the published German Patent Application No. 1,467,442 by Bayer A.G.

The unprocessed or uncoated pyrogenic TiO pigment is preferably obtained as burner discharge from a conversion unit in which gaseous TiCl -is reacted with oxygen at a temperature in excess of 800C. and in the presence of aluminum chloride.

In one method a TiO burner discharge is added to water to form a slurry containing -35% TiO and to this slurry is added a dispersant solution containing sodium hydroxide and sodium hexametaphosphate for the purpose of increasing the fluidity of the slurry so as to prevent blockage in the pulp tank lines and pumps; and also to neutralise the hydrochloric and hypochlorous acids present in the slurry-the dispersant being added at a rate to yield about 0.2% sodium hexametaphosphate on a pigment weight basis'and a pH of about 8.0 In addition to the dispersant an antichlor reducing agent solution, i.e., sodium sulphite may be added to destroy hypochlorites which are corrosive at concentration greater than about 35 p.p.m.--the reaction between the sodium sulphite and hypochlorite producing harmless reaction products i.e. sodium sulphate and sodium chloride. The pigment is then filtered, washed substantially free of soluble sodium salts, and reslurried.

Following the above described treatmentthe pigment slurry is pumped to storage tanks and from thence to the treatment sections of the plant whererthe pyrogenic TiO is diluted with water and is coated with a combination of the hydrous oxides of aluminum and silicon, for imparting the desired. photochemical inertness thereto. 1 1

The hydrous oxides used to coat the pyrogenic TiO pigment are those of silicon and aluminum exclusively and these may be precipitated on to the pigment successively or simultaneously. In thelatter instance the respective oxides may be used instoichiometric proportions such as to form hydrous'aluminum silicate, the term alumina-silica coating as used-hereinafter being comprehensive of an admixture of silica and alumina or LII a coating of hydrous aluminum silicate. It is essential moreover, that after deposition of the hydrous oxides on the pigment the coated pigment be calcined at a temperature sufficient to atleast partially dehydrate the hydrous oxide coating, i.e., remove at least some of the chemically combined water. Such partial dehydration may be effected by calcining the coated pigment, preferably for from 1 to 3 hours, at a temperature of at least 200C. for example, at temperatures within the range of from 200650C.

In general, the coated pyrogenic TiO pigments are prepared by admixing an aqueous slurry of pyrogenic TiO pigment, the slurry comprising, for example, 20 to 35% TiO with aqueous solutions of ionizable compounds of aluminum and-silicon. These ionizable compounds may be added in a ratio such that the hydrous oxides of aluminum and silicon are in the weight ratio of 2:1 with the total oxide coating comprising about 6% by weight of the TiO pigment. However, the 2: 1 weight ratio of alumina and silica is not critical and weight ratios of alumina and silica from 1:1 to 4:1 may be used, while the total amount of oxides may vary from 2 to 15% by weight of the TiO It is preferable when making the silica-alumina coated pigments that a silicate be used as the silicon compound and that the silicate solution be added before the aluminum compounds. This order of addition is preferred since the silicate solution serves to disperse the TiO in the slurry so that when the aluminum com.- pound is added the precipitated alumina and silica, or aluminum silicate, as the case may be, coats an optimum number of discrete TiO particles. Moreover, by adding the aluminum compound last it serves to coagulate the TiO slurry and hence facilitates filtering and washing the coated pigment.

Aluminum compounds which have been found satisfactory incl ude aluminum sulphate, aluminum nitrate, and aluminum chloride, as well as various aluminates including sodium aluminate and potassiumaluminate. Since the aluminates are highly alkaline, it will be necessary in such cases to acidify the slurry to a pH of about 7.0 after treatment.

The hydrous silica may be derived from any soluble silicate such as for example, sodium, potassium and ammonium silicates. However, for reasons of economy and availability sodium silicate and preferably sodium meta silicate (Na O SiO is used.

One particular way in which the coated pyrogenic TiO pigment may be prepared is as follows: An aqueous slurry of pyrogenic titanium dioxideprepared as described above containing 1000 gm. of TiO; at 20% solids and having a pH of about 7.7 was treated with 200 m1 of sodium silicate solution containing 26.6 gm. of N OH and 20 gm. SiO The batch was heated to 60C. Then 400 ml. of an aluminum sulphate solution (equivalent to 40 gm. of alumina and 116 gm. of sulphuric acid) was added to the slurry. The batch was neutralized to a pH of 7.0 with 292 ml. of sodium hydroxide solution containing 60.5 gm. of N OH to precipitate a coating of the hydrous oxides of aluminum and silicon on the TiO The quantity of coating calculated'to give a 2:1 A1 0 to SiO weight ratio product, i.e. 4% A1 0,, and 2% SiO after calcination, was 6 percent of the weight of the titanium dioxide. The H SO /NaOH ratio was 1.21 compared to a theoretical of 1.23. The hydrous oxide coated pigment was further heated for 1 hour at 60C., filtered, washed relatively salt free with water, and dried at 120C. It was then partially dehydrated by calcining at 500C, dry milled and pulverized. p 1

Other procedures for coating an untreated pyrogenic TiO pigment may be used, such as, for example, one wherein the sodium silicate solution is alkalized prior to its addition to the pigment slurry and subsequent addition of aluminum sulphate solution, as a consequence of which an aluminum silicate gel,is formed on the pigment which is subsequently calcined; or by the simultaneous addition of aqueous solutions of alkalized sodium silicate and aluminum sulphate in stoichiometric proportions so as to form an aluminum silicate coating on the pigmentboth of the above described techniques being well within the knowledge of persons skilled in the art.

A preferred photographic light-sensitive monosheet material according to the present invention comprises in the given order a non-transparent flexible support, a light-sensitive silver halide emulsion layer, and a layer containing a.titanium dioxide pigment, which has been prepared according to the known sulphate or chloride process and on which hydrated aluminium oxide and/or hydrated silicon dioxide has been precipitated during anafter-treatment, the amount of hydrated aluminium oxide in respect of-the titanium dioxide varying between 0.5 and 20% by weight and the amount of hydrated silicon dioxide varying between 0.1 and 20% by weight. The pigment is used in an amount of preferably 9 to 25 g per sq.m, whereas the binder is used in an amount of preferably-0.5 to 3 g per sq.m. The material comprises at least one developing agent.

The composite sheet material has a very simple structure and is especially suited for the production of an image according to the silver complex diffusion transfer reversal process. The diffusion transfer reversal image is preferably formed in the outer part of the pigment layer and/or at the upper side thereof. The silver halidecomplexes can diffuse without any difficulties through the pigment layer. The resulting high-quality diffusion transfer reversal images can be viewed on a specially-white background, since thenegative image produced in the silverhalide emulsion layer is shielded very'well by the pigment particles. At the rear side of the resulting diffusion transfer reversal print the negativeimage is substantially invisible also since a non-transparent support is used. This support is preferably a paper support so that the diffusion transfer reversal print is suited very well for being written on at the rear side, as well as for being folded and stored.

The size of the titanium dioxide pigment particles is not very critical for the purpose of the present invention. lndeed,,coarse as well as extremely fine grains can be used. In general, the size of the particles varies between'0.05 and 05 pm. The pigment particles can be dispersed homogeneously in an aqueous solution of a hydrophiliccolloid, preferably gelatin; Yet, other colloids such as carboxymethyl cellulose, alginic acid, alginates, and mixtures of colloids are suited as well. In general,- optimal results are obtained with an amount of 12 to g of pigment and 'of l to 2 g of colloid per sq.m. In order to keep the large amount of pigment particles dispersed homogeneously in the aqueous'solution in spite of small amounts of hydrophilic colloid binder, large amounts of dispersing agent can often be used. So, a large amount of titanium dioxide particles can very well be dispersed homogeneously in an aqueous solution "of a small amount of gelatin, when amounts of saponin of approximatively 0.5 g to 12 g per .lOO g. of titanium dioxide are used as dispersing agent. All common dispersing agents for pigment particles can be used instead of saponin or in addition to saponin. Further examples of particularly suitable dispersing agents are i;a.-sodium hexametaphosphate, naphthalene sulphonate condensates having a high molecular weight, certain quaternary ammonium salts, and certain polyphosphates. 1

In spite of the presence of a pigment layer comprising 9 to 25 g of pigment per sq.m in a weight proportion in respect of the binder of 3 to 50, the development of the silver halide emulsion layer and the formation of the diffusion transfer reversal image occurso fast as a result of the presence of one or more developing agents in-the monosheet material, that very soon (approximatively 5 to 10 sec) after the material has been wetted with the alkaline processing liquid, the diffusion transfer reversal image becomes visible and reaches full and high density already after 15 to 20 seconds.

Another preferred photographic light-sensitive monosheet material according to the present invention, which is also suited for the silver salt diffusion transfer reversal process, comprises in the given order a flexible transparent support, an image-receiving layer containing substances promoting the conversion of diffusing silver halide complexes for the production of a visible image (these substances are called development nuclei hereinafter), a pigment layer comprising the treated titanium dioxide pigment and a hydrophilic colloid binder, the pigment and the binder of the pigment particles being present in amounts of 7-25 g per sq.m and 0.5 to 4 g per sq.m. respectively, and a light-sensitive silver halide emulsion layer, the maximum developed reflection density of which does not exceed 0.8. A material fulfilling I these requirements has been described e.g. in the published German Patent Application No. 1,961,030 as mentioned hereinbefore and in the United Kingdom Patent Specification No. l,297,l l5 filed Nov. 28, 1969 by Gevaert-Agfa N.V.

The presence of development nuclei for the production of 'a visible silver image from the non-developed diffusing silver halide complexes is not essential. It was found indeed that the pigment particles used can act themselves to a certain extent as development nuclei and that acceptable diffusion transfer reversal prints can be obtained without the use of special development nuclei. In general, a diffusion transfer reversal image obtained in this way is, rather faint, however. Improved results can. be obtained by the use of special development nuclei. All development nuclei,'physical aswell as chemical nuclei, known to those skilled in the art can be used. Suitable examples are the sulphides of heavy metals such as the sulphides of antimony, bismuth, cadmium, cobalt, lead, nickel, silver and zinc as well as mixturesthereof. Other suitable salts are the selenides, polysulphides, polyselenides, mercaptans and tin(ll)halid'e. Heavy metals or their salts as well as foggedsilver halide are suited likewise. The complex salts oflead and zinc sulphides can be used alone as well as combined with thioacetamide, dithiobiuret, and dithiooxamide. Heavy metals, preferably silver, gold, platinum, palladium, and mercury can be used in colloidal form. The noble metals are the most active ones among these metals.

The development nuclei can be incorporated into the pigment layer in the usual concentrations, preferably .in the outer part of the pigment layer (the inner part is the side facing the silver halide emulsion layer). The development nuclei can be incorporated into the outer part of the pigment layer by applying the pigment layer in two or more steps and incorporating the development nuclei into the coating composition of the outer part. Preferably, however, the development nuclei are applied to the upper side of the pigment layer. For this purpose e.g. a separate gelatin layer containing development nuclei is applied as an image-receiving layer to the surface of the pigment layer. According to the most preferred embodiment of the invention, the nuclei are applied without binder or with but very small amounts of binder e.g. gelatin, to the surface of the pigment layer. The development nuclei can also be applied to the surface of the pigment layer, by incorporating them into the processing liquid for the production of the diffusion transfer reversal image or into a supplementary liquid to be applied before or after the image-wise exposure, in the latter case preferably before the application of the alkaline processing liquid for the wetting of the monosheet material.

The support of the photographic light-sensitive composite sheet material of the invention may be any common flexible support. The supports can be non-transparent as described in the published GermanPatent treatment during its preparation. The translucent support can also be a hydrophobic polymer film support of a rather poor thickness, preferably of approximatively 0.05 to 0.2 mm. Suitable polymers for the preparation of such film supports are cellulose esters e.g. cellulose triacetate, polyesters, e.g. polyethylene terephthalate, polystyrene, and copoly(vinylchloride/vinyl acetate).

By non-transparent" is meant that the support is such that the negative image formed in the light-sensitive silver halide emulsion layer is substantially invisible through the support. This can be attained by the use of a support, which is not transparent by itself or which has been made non-transparent in the mass or by application of one or more non-transparent layers, e.g. a baryta layer or another white or coloured covering layer, to at least one side of the support. Although any common flexible hydrophobic film support e.g. a film foil made of cellulose ester such as cellulose triacetate or of polyethylene terephthalate can be used, preference is given, however, to a paper support. Such a paper support can be made non-transparent by incorporating into the paper mass during the preparation of the paper an opaque white or coloured pigment and/or by application of a white or coloured pigment coating e.g. a baryta coating to at least one side of the paper sheet, according to a process generally known in the field of paper manufacture. The non-transparent paper sheet may be opaque. When the support is sufficiently translucent, the exposure of the emulsion layer can be performed through the support.

In the light-sensitive materials according to the present invention any silver halide emulsion layer, preferably a gelatin silver halide emulsion layer can be used, provided, however, that the exposed silver halide can be developed sufficiently rapidly and that complexes of the non-exposed silver halide can be formed sufficiently rapidly to meet the requirements of the diffusion transfer reversal process. The silver halide emulsion can be sensitized chemically and spectrally according to any common and generally known method.

They silver halide emulsion can possess the desired sensitometric properties for line or screen work, i.e. a high gradation or such a composition, that it is suited for continuous tone reproduction.

[n a light-sensitive material with non-transparent support a relatively high-sensitive silver halide emulsion is used preferably to make possible an episcopical exposure.

The light-sensitive materials of the present invention can be used successfully for any type of document printing and also for radiography. So, any silver halide emulsion layer for the direct or indirect recording (by means of intensifying screens) of X-ray or 'y-ray diagrams can be used. In the case of an indirect recording an intensifying screen can be built-in in the photographic composite sheet material. Suitable intensification screens are known to those skilled in the art. They fluoresce. upon irradiation with an image-wise modulated X-ray or 'y-ray beam. The intensification screen can be built-in in one or several structural layers of the composite shee'tmaterial or it may constitute a separate additional layer. So it is possible to place a separate intensification screen during the exposure step in contact with the composite sheet material and then to remove it before the processing.

The light-sensitive silver halide emulsion layer, the pigment layer,'and the layer containing development nuclei, if applied at all, can be hardened at least partially. The resistance to abrasion of the diffusion transfer reversal image obtained is improved by the at least partial hardening of the outer layer. Of course, the hardening agent must be selected in-accordance with the hydrophilic colloid to be hardened. Suitable and generally known hardening agents for gelatin and similar colloids, which are used often for layers to be hardened, are formaldehyde, glyoxal, mucochloric acid, potassium alum and chrome alum. The hardening agent does not have to be incorporated into the layers to be hardened during the very preparation step, but it can be provided into any other layer, which is in waterpermeable relationship to the layer to be hardened, the hardening only occurring after the diffusion of the hardening agent to the latter layer. The hardening agent can also be incorporated into the alkaline processing liquid for carrying out the diffusion transfer reversal process or in another treatingliquid. Also latent hardening agents can be incorporated into the photographic composite material of the invention. Such latent hardening agents are only active within a specific pH-range, mainly the pl-Lrange of 'the usual alkaline processing liquids for carrying out the diffusion transfer reversal. Suitable latent hardening agents are described in the United Kingdom Patent Specification No. 962,483 filed Jan. 1, 1962 by Agfa Aktiengesellschaft and in the published German Patent Application No. 1,203,604 filed Jan; 15, 1964 by Agfa A.G.

ln addition to the above-mentioned layers a photographic light-sensitive composite sheet material according to the invention may comprise one or more possibly hardened layers such as a primary layer, an antihalation layer, an intermediate layer, a covering layer of a hydrophilic colloid e.g. a preferably hardened gelatin covering layer, an antistatic layer, a layer improving the adhesion of the two other layers etc.

A preferred light-sensitive photographic composite sheet material according to the invention also contains at least one developing agent. The developing agent(s) should be in water-permeable relationship to the emulsion layer and consequently also to the element in which the diffusion transfer reversal image is produced. The developing agent(s) should be used in considerable amounts, i.e. preferably in amounts of at least approximatively 100 mg/sq.m of the composite sheet material so that they will substantially contribute to a fast image production by diffusion transfer reversal. Developing agents that are particularly suited for incorporation into the material are e.g. hydroquinone, 3- pyrazolidinones, ascorbic acid, p-aminophenols, and derivatives thereof. Combinations of two or more developing agents are often used. Preferably a mixture of hydroquinone and 1-phenyl-3-pyrazolidinone preferably in amounts beyond 200 mg and approximatively 50 mg respectively is used. The alkaline processing liquid may also contain a part of the developing agent(s), e.g. up to 17 g per liter. According to a preferred embodiment, however, the total amount of the developing agent(s) is comprised in the composite sheet material (approximatively 100 to 500 mg/m of the composite sheet material), so that the processing liquid can be reduced to a mere alkaline aqueous liquid, which is essentially free from developing agents and has optimal keeping qualities. Such a liquid is also called activator liquid.

A light-sensitive photographic composite sheet material according to the present invention can also contain one or more other substances that are necessary for carrying out the silver complex diffusion transfer reversal process or which are advantageous, as well as other common additives such as preservatives for the developing agents, toning agents, anti-yellowing compounds, optical brighteners, anticurling agents, stabilizing agents, spectral sensitizing agents for silver halide, plasticizers, hardening agents, especially latent hardening agents, pig'ments, latices, dispersing agents, antihalation dyes etc. All these substances are employed in the usual concentrations as can be found in the literature. The anti-yellowing compounds that are suited for incorporation into the composite sheet material, preferably into the pigment layer are 3-hydroxypropylene sulphite, pentaerythritol disulphite, triethanolamine sulphite hydrochloride, hexaethyl tetraphosphate, potassium ascorbic acid borate, hypophosphorus acid, and benzoic acid.

The production of a silver image according to the silver complex diffusion transfer reversal process in which a black-and-white photographic light-sensitive composite sheet material essentially as described hereinbefore is used, comprises the steps of the image-wise exposure of the silver halide emulsion layer of the composite material and the treatment of the material with an aqueous alkaline processing liquid in the presence of a developing agent and a complexing agent for silver halide, development nuclei being provided in the pigment layer and/or at the surface thereof.

The image-wise exposure of the silver halide emulsion layer can be performed in different ways. In the light-sensitive materials distinction has to be made between those having a non-light-transmitting support and those having a transparent support. When a nonlight-transmitting support is used, the exposure must be carried out through the pigment layer and may be a direct optical exposure in a camera, a contact exposure 12 through a transparent original, or an episcopical exposure.

When a light-sensitive material with a transparent support is used, the exposure can be a direct optical exposure in a camera, a contact exposure to a transparent original, an episcopical or a reflectographic exposure. For instance in the case of a contact exposure through a transparent support the image side of a one side-printed original is brought in contact with the emulsion side of the composite material, or the nonimage side of a one side-printed original is brought in contact with the support side of the composite material. In both cases the exposure is performed through the original.

When an episcopical exposure is used, originals printed at both sides can be taken and when a suitable optical system is chosen, directly legible images can be produced. Either the support side or the front side of the composite sheet material may face the original.

According to a certain embodiment of the reflectographic exposure the original, which may be an original printed on both sides, is pressed with the image side against the emulsion side of the material and the exposure is performed by means of a light source, which sends light through the transparent support, the white pigment layer, and the silver halide emulsion layer and finally then strikes the original. The light reflected image-wise by the original then reaches the silver halide emulsion layer again. The reflectographic exposure is suited very well for the fast printing of any kind of documents and texts from books and journals.

For easiness sake preference is given to a reflectographic exposure in the case of portable copying apparatuses, the so-called mini-copying apparatuses. The composite image material is extremely well suited therefor. For this purpose it is used preferably in roll form and cut to the desired formats inside or outside the copying apparatus.

After the photographic composite material has been exposed image-wise, it can be wetted with an alkaline processing liquid.

This wetting can be performed in whatever way e.g. by dipping of the composite sheet material in the alkaline processing liquid, by one side wetting by means of a roller, by bringing in contact with an object soaked with an alkaline processing liquid, by spraying, and by spreading of a viscous or non-viscous liquid, which may be contained e.g. in a pod or container. This method is known to those skilled in the art. The pod may be mounted on the surface of the composite material or may be provided e.g. between the non-transparent support and the silver halide emulsion layer or between the latter emulsion layer and the pigment layer.

The alkaline processing liquid may contain a part of the developing agents and preferably comprises the complexing agent for the unexposed silver halide. An especially suitable alkaline substance for making a processing liquid, which does not give rise to crystallization stains on the composite material, is diethanolamine, either or not buffered with trisodium phosphate.

The processing liquid may also contain other reagents such as a viscous film-forming material e.g. sodium carboxymethylcellulose, hydroxyethylcellulose, etc., preserving agents, antifogging agents, etc.

The alkaline processing liquid may also contain the development nuclei as described hereinbefore. During the wetting of the photographic composite sheet material the development nuclei deposit mainly on the surface of the pigment layer or of a hydrophilic colloid layer applied thereto, where the diffusion transfer reversal image is then produced. The development nuclei can also be applied from another liquid composition, by means of which the photographic composite material can be wetted before or after the exposure, preferably after the exposure and in this particular case preferably before the treatment with the alkaline processing liquid for carrying out the silver complex diffusion transfer reversal process. Such other liquid composition may contain the developing agent(s), which according to the invention have to be present in the composite sheet material.

Shortly after the wetting of the photographic composite material with the alkaline processing liquid a diffusion transfer reversal image of high quality appears at the side of the pigment layer, which is opposite to that of the support i.e. on the white titanium dioxidecoloured background, through which the negative image in the silver halide emulsion layer cannot be viewed or but very faintly. Moreover, the print obtained is almost immediately dry after the diffusion transfer reversal image has been formed so that the print can be used or stored immediately. Especially, when a paper support is used, the print can be folded easily and its rear side can be written on readily.

A copying apparatus that is suited for the exposure and the processing of the photographic composite sheet material according to the invention is described in the Belgian Patent Specification No. 716,310 filed June 10, 1968 by Gevaert-Agfa N.V.

With a panchromatically sensitized photographic material according to the invention colour separation images can be produced from colour diapositives or reflectographic originals. The colour separation images are separation positives, which have been made according to the silver complex diffusion transfer reversal process.

The separation positives are made by means of colour separation filter exposures or a red filter-green filter, and blue filter-exposure. For the production of a black separation image there can be exposed e.g. successively through the three filters.

For the exposures a masking process can be chosen, according to which the mask is applied e.g. in the camera. The colour separation filters have to be adapted not only to the light-sensitive separation materials but also to the printing colours.

Depending on whether screened colour separation images or continuous tone separation images have to be made, a screen is either used or not in the exposure.

it is known that during the exposure through the screen, the latter screen is turned through a given angle to counteract the moire-effect. For instance during the exposure through the blue filter a reference position of 90 is taken and during the exposures throughthe green filter and the red filter the screen is turned through 45 to the left and through 45 to the right respectively.

For the screen exposures e.g. a magenta screen is used for the blue filter exposure and a grey screen for the green filter and red filter exposures.

The separation positives can be used successfully e.g. for the xerographic production of multicolour images. The exposures should be carried out in register, of course, in the xerographic apparatus. After the exposure of the xerographic material with the red filter separation positive a charge image development with a cyan toner is performed. The exposures with the green filter separation positive and the blue filter separation positive correspond with a development with a magenta and a yellow toner respectively.

Although the process according to the invention has been described detailedly with the example of the silver salt diffusion transfer reversal process, according to which black-and-white images are obtained, the titanium dioxide pigments modified according to the invention are equally suited for the manufacture of white pigment layers in colour photographic monosheet materials for the production of m0noor multicolour images. Such multicolour monosheet materials usually comprise three differently sensitized silver halide emulsions in the light-sensitive part of the monosheet. Each silver halide emulsion layer comprises a colour-forming compound for the production of a separation colour image, whose colour is complementary to that of the light recorded in the silver halide emulsion layer. Suitable colour-forming compounds are e.g. the developing dyes described in the German-Patent Specification No. 1,196,075 filed Mar. 9, 1955 by Intern. Polaroid Corp., which are capable of migrating in the alkaline medium and are immobilized at the exposed areas as a result of t the reaction with exposed silver halide. Other suitable colour-forming compounds are non-diffusing dyes or colour couplers, which upon reaction with the oxidation products of developing agents split off diffusing dyes. In this respect there can be referred e.g. to the German Patent Specification No. 1,095,] 15 filed Aug. 8, 1958 by Eastman Kodak Co. and to the published German Patent Applications No. 1,930,215 filed June 13, 1969 by Agfa-Gevaert A.G. and No. 1,772,929 filed July 24, 1968 by Int. Polaroid Corp.

An image-receiving layer is provided also which is suited for fixing the diffusing dyes. Between the lightsensitive silver halide emulsion layers and the imagereceiving layer there is a non-light-transmitting layer, which at least at the side facing the image-receiving layer is composed so as to reflect light thanks to the use of the titanium dioxide pigment modified according to the invention, or a medium for making such a layer is provided, e.g. by mounting at the side of the multicolour monosheet material a pressure-rupturable container or pod comprising the treated titanium oxide pigment in paste form, which pod as a result of pressure exerted thereon spreads its contents between the image-receiving material and the light-sensitive silver halide emulsion layers, thus forming an appropriate non-light-transmitting pigment layer.

We claim:

l. in a photographic diffusion transfer reversal process in which a photo-sensitive silver halide emulsion layer is exposed and developed to form a visible negative silver image in the emulsion layer and to transfer either a silver halide complex or a dye to an image receiving layer to make a silver image or dye image visible against a white pigment background layer covering said negative silver image wherein said silver halide emulsion layer forms part ofa monosheet material comprising in order, either A. a non-transparent support, a silver halide emulsion layer, a pigment layer or means for applying a pigment layer and an image receiving layer or B. a transparent support, an image receiving layer, a

pigment layer or means for applying a pigment layer, and a silver halide emulsion layer, the improvement whereinthe pigment particles of the pigment layer consist essentially of white titanium dioxide pigment particles that havebeen modified by precipitation thereon of hydrated aluminum oxide alone or in admixture with hydrated silicon dioxide.

2. Process according to claim 1, wherein said lightsensitive silver halide emulsion layer is exposed imagewise and treated with an aqueous alkaline processing liquid in the presence of a developing agent and said white modified titanium dioxide pigment is applied from the processing liquid. 1

3. Process according to the claim 1, wherein th titanium dioxide pigment has the rutile or anatase structure.

4. Process according to claim 1, wherein the modified titanium dioxide pigment contains hydrated aluminium oxide (calculated in the form of A1 0 in an amount of 0.5 to by weight in respect of the tita nium dioxide.

5. Process according to claim l,wherein the modified titanium dioxide pigment comprises in addition to the hydrated aluminium oxide hydrated silicon dioxide (calculated in' the form of SiO in an amount of 0.1 to 20% by weight in respect of the titanium dioxide.

- 6. Process according to claim 1, wherein the size of the pigment particles is between 0.05 and 0.5 pm.

7. Process according to claim 2, wherein substantially the total amount of developing agent for developing said exposed emulsion layer is contained in the photographic-monosheet material and said aqueous alkaline processing liquid is substantially free from developing agents.

8. Process according to claim 2, wherein the aqueous alkaline processing liquid comprises an agent increas ing its viscosity.

9. Process according to claim 2, wherein development nuclei are supplied to at least the surface of the pigment layer from a liquid applied after the imagewise exposure.

10. In a photographic supported monosheet material adapted for the production of a visible transfer image on a white background by diffusion transfer of either silver halide complexes or dyes,- which material comprises in order a non-transparent support, a silver halide emulsion layer, a pigment layer or means for applying a pigment layer, and an image receiving layer, the improvement wherein the pigment particles of said pigment layer or means for applying said pigment layer consist essentially of white titanium dioxide pigment particles that have been modified by precipitation thereon of hydrated aluminum oxide or of hydrated aluminum oxide together with hydrated silicon dioxide.

11. Photographic material according to claim 10, wherein a titanium dioxide pigment and the binder for the pigment particles are present in amounts of 9 to g per sq.m and 0.5" to 3 g per sq.m respectively, the material containing at least one developing agent.

12. Photographic material according to claim 11, containing hydroquinone and a l-phenyl-3-pyrazolidinonecompound as developing agents.

1'3. Photographic material according to claim 12, wherein the developing agents are used in amounts of approximatively mg to approximatively 500 mg per sq.m.

l4. Photographic material according to claim 10,

containing at least one spectrally sensitized silver halide emulsion layer.

15. Photographic material according to claim 10, wherein the support is a paper support, which has been made non-transparent in the mass or by application thereto of a non-transparent coating.

16. Photographic material according to claim 10, wherein the support is a hydrophobic polymer film support.

17. Photographic material according to claim 10, wherein development nuclei are provided in the at least the surface of the pigment layer.

18. In a photographic supported monosheet material adapted for the production of a visible transfer image on a white background by diffusion transfer of either silver halide complexes or dyes, which material comprises in order a transparent support, an image receiving layer, a pigment layer or means to apply a pigment layer and the silver halide emulsion layer, the improvement wherein the pigment particles of said pigment layer or means for applying said pigment layer consist essentially of white'titanium dioxide pigment particles that have been modified by precipitation thereon of hydrated aluminum oxide or of hydrated aluminum oxide together with hydrated silicon dioxide.

19. Photographic material according to claim 18, wherein the titanium dioxide pigment and a binder for the pigment particles are present in amounts of 9-25 g per sq.m and 0.5 to 3 g per sq.m respectively, the material containing at least one developing agent.

20. Photographic material according to claim 19, containing hydroquinone and a l-phenyl-3-pyrazolidinone compound as developing agents.

21. Photographic material according to claim 20,

wherein the developing agents are used in amounts of approximately 100 mg to approximately 500 mg per sq.m.

22. Photographic material according to claim 18, successively having a flexible transparent support, an image-receiving layer containing development nuclei, a layer containing the modified titanium dioxide pigment and a colloid binder.

23. Photographic material according to claim 18, containing at least one spectrally sensitized silver halide emulsion layer.

24. Photographic material according to claim 18, wherein the support is a hydrophobic polymer film support.

25. Photographic material according to claim 18, wherein development nuclei are provided in at least the surface of the pigment layer.

Disclaimer 3,928,037.L0uis M aria De Haes, Edegem, Belgium, and Hams-Georg Vb'lz,

Krefeld-Bockum, Germany. TITANIUM DIOXIDE WITH ALU- MINUM OXIDE OR ALUMINUM OXIDE PLUS SILICON DIOXIDE PREOIPITATED THEREON AS PIGMENT FOR DIFFUSION TRANSFER. Patent dated Dec. 23, 1975. Disclaimer filed Dec. 12, 1977, by the assignee, A g fa-G'e'vaert N.V.

Hereby enters this disclaimer to claims 125 of said patent.

[Ojficz'al Gazette Apr-2118, 1.978.] 

1. IN A PHOTOGRAPHIC DIFFUSION TRANSFER REVERSAL PROCESS IN WHICH A PHOTO-SENSITIVE SILVER HALIDE EMULSION LAYER IS EXPOSED AND DEVELOPED TO FORM A VISIBLE NEGATIVE SILVER IMAGE IN THE EMULSION LAYER AND TO TRANSFER EITHER A SILVER HALIDE COMPLEX OR A DYE TO AN IMAGE RECEIVING A LAYER TO MAKE A SILVER IMAGE OR DYE IMAGE VISIBLE AGAINST A WHITE PIGMENT BACKGROUND LAYER COVERING SAID NEGATIVE SILVER IMAGE WHEREIN SAID SILVER HALIDE EMULSION LAYER FORMS PART OF A MONOSHEET MATERIAL COMPRISING IN ORDER, EITHER A. A NON-TRANSPARENT SUPPORT, A SILVER HALIDE EMULSION LAYER A PIGMENT LAYER OR MEANS FOR APPLYING A PIGMENT LAYER AND AN IMAGE RECEIVING LAYER OR B. A TRANSPARENT SUPPORT AN IMAGE RECEIVING LAYER, A PIGMENT LAYER OR MEANS FOR APPLYING A PIGMENT LAYER, AND A SILVER HALIDE EMULSION LAYER, THE IMPROVEMENT WHEREIN THE PIGMENT PARTICLES OF THE PIGMENT LAYER CONSISTS ESSENTIALLY OF WHITE TITANIUM DIOXIDE PIGMENT PARTICLES THAT HAVE BEEN MODIFIED BY PRECIPITATION THEREON OF HYDRATED ALUMINUM OXIDE ALONE OR IN ADMIXTURE WITH HYDRATED SILICON DIOXIDE.
 2. Process according to claim 1, wherein said light-sensitive silver halide emulsion layer is exposed image-wise and treated with an aqueous alkaline processing liquid in the presence of a developing agent and said white modified titanium dioxide pigment is applied from the processing liquid.
 3. Process according to the claim 1, wherein the titanium dioxide pigment has the rutile or anatase structure.
 4. Process according to claim 1, wherein the modified titanium dioxide pigment contains hydrated aluminium oxide (calculated in the form of Al2O3) in an amount of 0.5 to 20% by weight in respect of the titanium dioxide.
 5. Process according to claim 1, wherein the modified titanium dioxide pigment comprises in addition to the hydrated aluminium oxide hydrated silicon dioxide (calculated in the form of SiO2) in an amount of 0.1 to 20% by weight in resPect of the titanium dioxide.
 6. Process according to claim 1, wherein the size of the pigment particles is between 0.05 and 0.5 Mu m.
 7. Process according to claim 2, wherein substantially the total amount of developing agent for developing said exposed emulsion layer is contained in the photographic monosheet material and said aqueous alkaline processing liquid is substantially free from developing agents.
 8. Process according to claim 2, wherein the aqueous alkaline processing liquid comprises an agent increasing its viscosity.
 9. Process according to claim 2, wherein development nuclei are supplied to at least the surface of the pigment layer from a liquid applied after the image-wise exposure.
 10. In a photographic supported monosheet material adapted for the production of a visible transfer image on a white background by diffusion transfer of either silver halide complexes or dyes, which material comprises in order a non-transparent support, a silver halide emulsion layer, a pigment layer or means for applying a pigment layer, and an image receiving layer, the improvement wherein the pigment particles of said pigment layer or means for applying said pigment layer consist essentially of white titanium dioxide pigment particles that have been modified by precipitation thereon of hydrated aluminum oxide or of hydrated aluminum oxide together with hydrated silicon dioxide.
 11. Photographic material according to claim 10, wherein a titanium dioxide pigment and the binder for the pigment particles are present in amounts of 9 to 25 g per sq.m and 0.5 to 3 g per sq.m respectively, the material containing at least one developing agent.
 12. Photographic material according to claim 11, containing hydroquinone and a 1-phenyl-3-pyrazolidinone compound as developing agents.
 13. Photographic material according to claim 12, wherein the developing agents are used in amounts of approximatively 100 mg to approximatively 500 mg per sq.m.
 14. Photographic material according to claim 10, containing at least one spectrally sensitized silver halide emulsion layer.
 15. Photographic material according to claim 10, wherein the support is a paper support, which has been made non-transparent in the mass or by application thereto of a non-transparent coating.
 16. Photographic material according to claim 10, wherein the support is a hydrophobic polymer film support.
 17. Photographic material according to claim 10, wherein development nuclei are provided in the at least the surface of the pigment layer.
 18. In a photographic supported monosheet material adapted for the production of a visible transfer image on a white background by diffusion transfer of either silver halide complexes or dyes, which material comprises in order a transparent support, an image receiving layer, a pigment layer or means to apply a pigment layer and the silver halide emulsion layer, the improvement wherein the pigment particles of said pigment layer or means for applying said pigment layer consist essentially of white titanium dioxide pigment particles that have been modified by precipitation thereon of hydrated aluminum oxide or of hydrated aluminum oxide together with hydrated silicon dioxide.
 19. Photographic material according to claim 18, wherein the titanium dioxide pigment and a binder for the pigment particles are present in amounts of 9-25 g per sq.m and 0.5 to 3 g per sq.m respectively, the material containing at least one developing agent.
 20. Photographic material according to claim 19, containing hydroquinone and a 1-phenyl-3-pyrazolidinone compound as developing agents.
 21. Photographic material according to claim 20, wherein the developing agents are used in amounts of approximately 100 mg to approximately 500 mg per sq.m.
 22. Photographic material according to claim 18, successively having a flexible transparent support, an image-receiving layer coNtaining development nuclei, a layer containing the modified titanium dioxide pigment and a colloid binder.
 23. Photographic material according to claim 18, containing at least one spectrally sensitized silver halide emulsion layer.
 24. Photographic material according to claim 18, wherein the support is a hydrophobic polymer film support.
 25. Photographic material according to claim 18, wherein development nuclei are provided in at least the surface of the pigment layer. 